J. Anim Sci. 2007. 85:1086-1091. doi:10.2527/jas.2006-493
© 2007 American Society of Animal Science
Longevity and efficiency associated with age structures of female pigs and herd management in commercial breeding herds1
Y. Koketsu2
School of Agriculture, Meiji University, Kawasaki 214-8571 Japan
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Abstract
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Annual performance measurements, age structures of female pig inventories, and by-parity culling rates were abstracted from data files of 110 herds that participated in a data-share program in Japan. Parity at culling was used as a prime measurement of longevity, whereas pigs weaned·mated female–1·year–1 (PWMFY) was a prime measurement of reproductive efficiency. High or low longevity herds were based on the greatest 50% of the herds or the remaining herds ranked by parity at culling, whereas high or low reproductive efficiency herds were grouped according to the greatest 50% of the herds or the remaining herds ranked by PWMFY. Measurements were analyzed as a 2 x 2 factorial arrangement, using the main effects of the 2 herd groups of longevity (high or low) and reproductive efficiency (high or low). Means of parity at culling and PWMFY were 4.6 (SD = 0.82) and 21.2 (SD = 3.02), respectively. The high longevity group had 1.27 greater parities at culling than the low longevity group (P < 0.05), but no differences between the high and low longevity groups were found in PWMFY (P = 0.21). No differences between the high and low efficiency groups were found in parity at culling (P = 0.50). No interactions between the longevity and efficiency groups were found on any longevity or efficiency measurement (P > 0.20). In herd management, the percentage of reserviced females and the percentage of multiple matings were associated with the longevity group and the efficiency group (P < 0.05). The high longevity group had lower culling rates in parity 0 to 6 than the low longevity group (P < 0.05), whereas no differences between the low and high efficiency groups were found in culling rates in parity 0 to 2 (P > 0.20). This study suggests that measures to achieve longevity and high reproductive efficiency in breeding herds do not conflict and that high reproductive efficiency and high longevity can be achieved.
Key Words: management • reproductive productivity • sow longevity • welfare
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INTRODUCTION
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Short longevity in female pigs increased expenses for gilt replacements and created subpopulations of low parity animals with low disease resistance (Deen, 2003
). Both longevity and optimum reproductive efficiency are critical for producers managing commercial herds. Characteristics of high efficiency herds have been studied to identify benchmarks for the swine industry (Stein et al., 1990; Koketsu, 2000), but the characteristics of herds with high longevity and efficiency have not been reported. Herd management variables have been monitored to improve reproductive efficiency of a herd (King et al., 1998) but have not been well applied to improve female longevity.
The mean parity of culled females has been used as a measurement of sow longevity (Lucia et al., 1999) because recording female age is not common in the swine industry. Parity of farrowed sows, average herd parity, female death rate, culling rate, and lifetime pigs weaned per culled females have also been used for longevity measurements (Stein et al., 1990). Improvement goals for longevity and age measurements for producers and veterinarians have not been reported in the swine industry.
The means of herd measurements can be influenced by a high frequency of low or high values within a herd. In particular, age structures in the female inventory and by-parity culling rates are considered to be more informative than annual culling rates (D’Allaire and Drolet, 1999) and herd size. However, age structures and by-parity culling rates within a herd were not measured in relation to female longevity and herd efficiency. A relationship between by-parity culling rate, longevity, and reproductive efficiency measurements was also not reported.
The objectives of this study were to observe longevity characteristics in herd performance, management measurements, within-herd age structures, and by-parity culling rates, and to determine a relationship between by-parity measurements, longevity, and reproductive efficiency.
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MATERIALS AND METHODS
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Animal Care and Use Committee approval was not obtained for this study because the data were obtained from our Data Share Program.
Data Share Program
A data share program using a recording software (PigCHAMP) was established in 2001 with swine producers in Japan. All producers using PigCHAMP were requested to mail their data files to the School of Agriculture, Meiji University, every time they renewed the yearly maintenance contract. The information on the herd record was held under strict confidence. Participants in the data share program were provided a summary of the standard and the improvement goal for their herd productivity. Data in this study included approximately 1.4% of all Japanese herds and approximately 5% of female inventories in Japan. Japan had 7,770 breeding herds and 917,000 females in February 2004 (MAFF, 2005).
Data Selection
Of approximately 140 herds using PigCHAMP in Japan, 122 mailed the production records to the university between May 1 and July 25, 2005. Of the participating 122 herds, 5 herds were omitted because they were grow-finish operations. To be included in the study, herds had to have stable female inventories and consistent data recording. A data integrity analysis from January 1 through December 31, 2004, was performed on each herd file to check for missing records and changes in herd size. Of the 117 breeding herds, the records for 6 herds were omitted because those herds were newly established, whereas 1 herd had more than 10% missing records. Hence, 110 herds were selected for further analysis. Annual performance and by-parity measurements from parity 0 to 
7 during the 12 mo of 2004 were extracted from the records of each herd.
Definitions and Calculations
Females included maiden gilts, mated gilts, and sows (PigCHAMP, 1996). Maiden gilts were defined as female pigs that entered the breeding herd but were not yet mated. The average female inventory (pig years) was calculated as the total days that females were fed in a herd during 1 yr divided by 365 d (Stein et al., 1990; Friis and Seller, 2004). Within-herd age structure of females for 1 yr was measured as the proportion of females in each parity between 0 and 7 in the average female inventory. The gilt pool size was defined as the proportion of the number of maiden gilts in the female inventory.
Parity at culling was used as a prime measurement of longevity (Lucia et al., 1999), whereas pigs weaned·mated female–1·year–1 (PWMFY) was the prime measurement of reproductive efficiency in breeding herds (Dial et al., 1992). Nonproductive days were the average number of days when mated females were neither gestating nor lactating (Stein et al., 1990).
Parity of farrowed sows, average herd parity, and female death rate were also considered as age measurements. Average herd parity was defined as the average parity of the female inventory at the end of the year. Culling rate (in %), replacement rate (in %), lactation length (in days), preweaning mortality (in %), and proportions of multiple mating, sows mated by 7 d after weaning, and reserviced females were used as herd-management measurements.
Culled females included females shipped to the slaughterhouse or destroyed in the barn. The culling rate was defined as the number of culled females divided by the average female inventory. For a by-parity culling rate in each parity group, the number of culled females was divided by the average female inventory in the parity group. The replacement rate was defined as the number of replacement gilts divided by the average female inventory. The female death rate was defined by the number of dead female pigs multiplied by 100 and then divided by the average female inventory.
Herd Ranking and Grouping
Herds were ranked and grouped according to the parity at culling, for longevity, and the PWMFY, for reproductive efficiency. High or low longevity herds were based on the greatest 50% of the herds or the remaining herds ranked by the parity at culling, whereas high or low efficiency herds were grouped according to the greatest 50% of the herds or the remaining herds ranked by the PWMFY.
Statistical Analysis
The observational unit was the herd. All analyses were conducted using SAS (SAS Inst. Inc., Cary, NC). Correlation analysis of parity at culling and PWMFY with other measurements was performed. Measurements of longevity, reproductive efficiency, herd management, age structures of the females, and by-parity culling rates were subjected to ANOVA for an observational study with a 2 x 2 factorial arrangement, using the main effects of the 2 herd groups of longevity (high or low) and efficiency (high or low) in the MIXED procedure. Means for the 2 main effects were compared. A log transformation was done for average female inventory; transformed data (means and SE) were back-transformed to present the results. Herd locations in Japan were grouped into 5 regional blocks. The regional blocks were used as random effects in this study because a random sample of a large set of population levels was used.
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RESULTS
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Means of parity at culling and PWMFY were 4.6 and 21.2 pigs of 110 herds, respectively (Table 1). Parity at culling was not related to efficiency measurements such as PWMFY (P > 0.05) but was positively correlated with other age measurements (P < 0.05) except for female death rate. Lower culling rates from parity 0 to 2 were correlated with parity at culling (P < 0.05), but were not correlated with PWMFY.
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Table 1. Summary statistics of key measurements and correlations between longevity and reproductive efficiency in 110 breeding herds
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The high longevity group had 1.27 greater parities at culling than the low longevity group (P < 0.05), but no differences between the high and low longevity groups were found in the efficiency measurements (P > 0.15; Table 2). In contrast, the high efficiency group had 4.6 more PWMFY than the low efficiency group (P < 0.05), but no differences between the high and low efficiency groups were found in parity at culling (P = 0.50). The high longevity group and the high efficiency group had greater lifetime pigs weaned per culled female than the counterpart groups (P < 0.05). No interactions between the 2 effects of the longevity and efficiency groups were found for any efficiency and longevity measurement (P > 0.20).
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Table 2. Comparisons of longevity and efficiency between high-performing herds based on the greatest 50% of the herds (high) and the remaining herds (low) ranked by parity at culling (longevity) or pigs weaned·mated female–1·year–1 (efficiency)
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In herd-management measurements (Table 3), the percentage of reserviced females and the percentage of multiple matings were associated with the longevity group and the efficiency group (P < 0.05). The high longevity group had lower percentages of culling and replacement than the low longevity group (P < 0.05), but had no differences in the other management measurements from the low longevity groups. The high efficiency group had a greater farrowing rate, and a greater percentage of sows mated by 7 d after weaning than the low efficiency group (P < 0.05).
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Table 3. Comparisons of herd-management measurements between high-performing herds based on the greatest 50% of the herds (high) and the remaining herds (low), ranked by parity at culling (longevity) or pigs weaned·mated female–1·year–1 (efficiency)
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The high longevity group had 10 to 20% lower culling rates in parity 0 to 3 than the low longevity group (Table 4; P < 0.05). No differences between the high and low efficiency groups were found in culling rates at parity 0 to 2 (P > 0.20). No interactions between the 2 herd groups were also found on age structures of females and by-parity culling rates (P > 0.20). Finally, Table 5 shows a summary of age measurements, age structures, and by-parity culling rates in 36 high-longevity and high-efficiency herds.
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Table 4. Comparisons in age structures of females and by-parity culling rates between high-performing herds based on the greatest 50% of the herds (high) and the remaining herds (low), ranked by mean parity at culling (longevity) or pigs weaned·mated female–1·year–1 (efficiency)
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Table 5. Summary of key measurements, age measurements, age structures of females, and by-parity culling rates in the high-longevity and high-efficiency herds based on the greatest 50% of the herds, ranked by mean parity at culling (longevity) and pigs weaned·mated female–1·year–1 (efficiency)
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DISCUSSION
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The mean of parity at culling was 4.6 in this study, which was within the range of culling at parity between 2 and 5 in a previous report that was broadly reviewed (D’Allaire and Drolet, 1999). The lack of a significant correlation between parity at culling and PWMFY in this study disagreed with a previous report that showed a positive relationship between parity at culling and reproductive efficiency (Dagorn and Aumaitre, 1979), but agreed with previous reports showing no relationships between parity at culling or average herd parity and reproductive efficiency measurements (Stein et al., 1990; King et al., 1998). These conflicting findings suggested that some farms had both high efficiency and high longevity, but other farms had either one or neither.
The findings in this study clearly indicated a difference in by-parity culling rates and culling management between the high longevity group and the low longevity group. The negative correlations between longevity and culling rates from parity 0 to 5 supported that low culling rates in low and midparities were logically necessary for longevity. More specifically, culling rates of lower than 20% at parity 0 and 1 would be recommended for producers aiming a high-longevity and high-efficiency herd.
Decreasing culling rates in low parity females can be achieved by developing good gilts with appropriate BW, medium backfat thickness, and sound legs (Rozeboom et al., 1996). Nutritional management in gilt development and gestation (Rozeboom et al., 1996; Young et al., 2004) and confirmations at selection (Tiranti and Morrison, 2006) are critical to raise gilt replacements. Additionally, feed intake during lactation for low parity sows should be maximized to meet their nutritional requirements (Eissen et al., 2003).
Measuring by-parity culling rates may be a good tool to control age structures of females. However, it is noteworthy that a decision on which females should be culled is more important than any culling rate (D’Allaire and Drolet, 1999). This study also indicated that producers managing a high-longevity and high-efficiency herd can increase lifetime productivity in sows and facilitate a concern of animal welfare.
Age structures within a breeding herd can also be managed by bringing in replacement gilts and culling nonpregnant sows at high parity (Koketsu, 2005). The age structures and by-parity culling rates in the high-longevity and high-efficiency herds are reasonable targets in the swine industry. Measurement of within-herd age structures and keeping the structures high and stable for improving female longevity are recommended.
The association of the percentage of reserviced females with both the longevity and the efficiency groups indicated that both longevity and efficiency were related with a reservice occurrence. This suggested that a decreasing occurrence of reproductive failure improved longevity and efficiency. A percentage of reserviced females can be improved by increasing lactation feed intake (Koketsu et al., 1996) and appropriate timing of mating with multiple matings (Xue et al., 1998). High-longevity and high-efficiency are attainable in commercial breeding herds. Management for decreasing a culling rate in low parity females is a primary factor to enhance high longevity.
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Footnotes
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1 Acknowledgments: Appreciation is expressed to the staff in Global Pig Farms Inc. (Setagun, Gunma, Japan) for their technical assistance and cooperative producers for providing their records. This research is supported by Research Project Grant from Meiji University and MEXT. HAITEKU. 
2 Corresponding author: koket001{at}isc.meiji.ac.jp
Received for publication July 23, 2006.
Accepted for publication November 23, 2006.
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LITERATURE CITED
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D’Allaire, S., and R. Drolet. 1999. Culling and mortality in breeding animals. Pages 1003–1016 in Diseases of Swine. 8th ed. B. E. Straw, S. D’Allaire, W. L. Mengeling, and D. J. Taylor, ed. Iowa State Univ. Press, Ames.
Deen, J. 2003. Sow longevity measurement. Proc. Allen D. Leman Swine Conf. 30:192–193.
Dial, G. D., W. E. Marsh, D. D. Polson, and J. P. Vaillancourt. 1992. Reproductive failure: Differential diagnosis. Pages 88–137 in Diseases of Swine. 7th ed. A. D. Leman, B. E. Straw, W. L. Mengeling, S. D’Allaire, and D. J. Taylor, ed. Iowa State Univ. Press, Ames.
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Abstract
INTRODUCTION
